Iowa's wet summer may have helped trigger salmonella outbreak

State College, Pa. AccuWeather.comreports a recall of 380 million eggs because of salmonella could be in part attributed to wet, humid weather across Iowa.

An increase in salmonella itself is not linked directly with weather and climate, but the rodent population responsible for spreading salmonella is influenced by changes in temperature, precipitation and season.

Very wet weather, humid conditions and seasonal changes bringing cooler temperatures can drive rodents into chicken houses, which act as a port of shelter from the elements.

"In the fall, when the weather turns cold, mice move into buildings," said Darrell Trampel, Iowa State University Professor of Veterinary Diagnostics.

Wright County Eggs of Galt, Iowa, where the recalled eggs have been traced, is in a region that has been inundated by above-normal rainfall this summer.

AccuWeather.com meteorologists note that Galt, Iowa, is in an area inflicted by rainfall 200 to 300 percent above normal since June 1. This translates into approximately 8-12 inches of extra rainfall for Galt this summer.

Cities around Galt, including Waterloo, Des Moines and Marshalltown, have had over 20 inches of rain since June 1. The Midwest has endured above-normal temperatures and extreme humidity this summer.

Excess rainfall could have caused more rodents to enter the chicken coops in Iowa, which could mean more salmonella infected droppings. The infected droppings could have contaminated the feed eaten by the chickens producing the eggs.

According to a Penn State College of Agricultural Sciences manual on food safety in the table egg industry, pest management is a critical control point for diminishing salmonella exposure in chickens.

"Rodents are the primary source of salmonella," said Trampel. "They bring it with them into the chicken houses."

The report said that rodents like mice and rats are among the leading causes of salmonella in chicken coops because their daily droppings can contain up to 230,000 salmonella bacteria.

When excreting, rodents often leave their droppings in feed troughs, on egg belts and in other areas where there is contamination of not only the egg, but the feed eaten by chickens.